FIELD OF THE INVENTION
The invention relates to a method for adjusting the load of an internal combustion engine, in particular for a motor vehicle, in which an opening angle of an electromotively adjustable throttle valve in an intake duct is derived from a position of an accelerator pedal, and the opening angle is limited to a rotational speed-dependent opening value.
The invention is based on a throttle valve controller in accordance with German Published, Non-Prosecuted Patent Application DE 42 23 253 A1. In that publication, a control unit (electronic engine power controller) is described which forms a setpoint value for the opening angle of the throttle valve, at least as a position of the accelerator pedal. The value serves as a reference variable for a position controller which actuates an electromotive actuator for setting the opening angle of the throttle valve.
In order to condition a mixture correctly, fuel-metering systems require precise information on the air mass sucked in per stroke by the internal combustion engine. They receive that information through a quick-reacting air mass sensor which operates, for example, according to the hot film principle. Due to its high response speed, the output signal of the air mass sensor follows each pulsation in the air stream. Even air masses which are flowing back are sensed, but with a negative sign.
Alternating forward flows and backward flows of the air in an intake duct of an internal combustion engine are referred to as pulsations.
As soon as such pulsations occur, the air mass sensor therefore no longer supplies any correct measured values which could be used for conditioning the mixture.
A method for reducing the pulsations in the region of the intake duct in which the air mass sensor is disposed is known from German Published, Non-Prosecuted Patent Application DE 42 39 842 A1. That method is based on the discovery that the backward flow has a fixed chronological relationship with the position of the crankshaft. Thus, the frequency of the backward flow of the air masses corresponds to the rotational speed of the internal combustion engine. In that method, the opening angle of the throttle valve is changed at every reversal in flow. Thus, it moves in the direction of "closing" in the case of backward flowing air masses and in the direction of "opening" in the case of forward flowing air masses.
The backward flow in the region of the intake tract which lies upstream of the throttle valve is thus damped. The disadvantage of that method is the very high actuation expenditure for the adjustment of the throttle valve directed counter to the backward flowing air masses.
In a system known from U.S. Pat. No. 4,781,162 for controlling the throttle valve of an internal combustion engine, a maximum opening angle is determined as a function of the rotational speed. The opening angle of the throttle valve is regulated so as to achieve minimum fuel consumption with the stipulation that the maximum opening angle is not exceeded. Abrupt changes in the power emission of the internal combustion engine are thus prevented.